package org.apache.lucene.search;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.util.ToStringUtils;

import java.util.Set;
import java.io.IOException;

/**
 * A query that matches all documents.
 *
 */
public class MatchAllDocsQuery extends Query {

    public MatchAllDocsQuery() {
        this(null);
    }

    private final String normsField;

    /**
     * @param normsField Field used for normalization factor (document boost). Null if nothing.
     */
    public MatchAllDocsQuery(String normsField) {
        this.normsField = normsField;
    }

    private class MatchAllScorer extends Scorer {
        final TermDocs termDocs;
        final float score;
        final byte[] norms;
        private int doc = -1;

        MatchAllScorer(IndexReader reader, Similarity similarity, Weight w, byte[] norms) throws IOException {
            super(similarity, w);
            this.termDocs = reader.termDocs(null);
            score = w.getValue();
            this.norms = norms;
        }

        @Override
        public int docID() {
            return doc;
        }

        @Override
        public int nextDoc() throws IOException {
            return doc = termDocs.next() ? termDocs.doc() : NO_MORE_DOCS;
        }

        @Override
        public float score() {
            return norms == null ? score : score * getSimilarity().decodeNormValue(norms[docID()]);
        }

        @Override
        public int advance(int target) throws IOException {
            return doc = termDocs.skipTo(target) ? termDocs.doc() : NO_MORE_DOCS;
        }
    }

    private class MatchAllDocsWeight extends Weight {
        private Similarity similarity;
        private float queryWeight;
        private float queryNorm;

        public MatchAllDocsWeight(Searcher searcher) {
            this.similarity = searcher.getSimilarity();
        }

        @Override
        public String toString() {
            return "weight(" + MatchAllDocsQuery.this + ")";
        }

        @Override
        public Query getQuery() {
            return MatchAllDocsQuery.this;
        }

        @Override
        public float getValue() {
            return queryWeight;
        }

        @Override
        public float sumOfSquaredWeights() {
            queryWeight = getBoost();
            return queryWeight * queryWeight;
        }

        @Override
        public void normalize(float queryNorm) {
            this.queryNorm = queryNorm;
            queryWeight *= this.queryNorm;
        }

        @Override
        public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
            return new MatchAllScorer(reader, similarity, this, normsField != null ? reader.norms(normsField) : null);
        }

        @Override
        public Explanation explain(IndexReader reader, int doc) {
            // explain query weight
            Explanation queryExpl = new ComplexExplanation(true, getValue(), "MatchAllDocsQuery, product of:");
            if (getBoost() != 1.0f) {
                queryExpl.addDetail(new Explanation(getBoost(), "boost"));
            }
            queryExpl.addDetail(new Explanation(queryNorm, "queryNorm"));

            return queryExpl;
        }
    }

    @Override
    public Weight createWeight(Searcher searcher) {
        return new MatchAllDocsWeight(searcher);
    }

    @Override
    public void extractTerms(Set<Term> terms) {
    }

    @Override
    public String toString(String field) {
        StringBuilder buffer = new StringBuilder();
        buffer.append("*:*");
        buffer.append(ToStringUtils.boost(getBoost()));
        return buffer.toString();
    }

    @Override
    public boolean equals(Object o) {
        if (!(o instanceof MatchAllDocsQuery))
            return false;
        MatchAllDocsQuery other = (MatchAllDocsQuery) o;
        return this.getBoost() == other.getBoost();
    }

    @Override
    public int hashCode() {
        return Float.floatToIntBits(getBoost()) ^ 0x1AA71190;
    }
}
